1. Field of the Invention
The present invention relates to a link type front suspension structure applied to a motorcycle.
2. Description of Background Art
A link type front suspension structure having a shock absorbing function not in a front fork but separately from a front fork, in which expansion and contraction of the front fork is conveyed to a shock absorber through a link mechanism, is known from the related art.
FIG. 8 shows a link type front suspension structure of the related art.
Specifically, a steering stem 101 is rotatably attached to a head pipe 100, a top bridge 102 is provided on an upper end of this steering stem 101, a bottom bridge 103 is provided on a lower end of the steering stem 101, a front fork 104 is supported by the top bridge 102 and the bottom bridge 103, one end of an axle support arm 105 is connected to a lower end of this front fork 104, and the other end of the axle support arm is connected to an axle 106 of a front wheel.
An upper end of a shock absorber 107 is attached to a cushion upper bracket passed through the front fork 104 and arranged on a lower end of the top bridge 102, a lower end of this shock absorber 107 is attached to a cushion arm 108 having one end pivoted on the bottom bridge 103, a push rod 109 links between the cushion arm 108 and the axle support arm 105, and expansion and contraction of the front form 104 is conveyed to the shock absorber 107 through a link mechanism made up of the axle support arm 105, the push rode 109 and the cushion arm 108.
With the above described link type front suspension structure of the related art, there is great variation between the direction of expansion and contraction of the front fork and the arrangement direction of the push rod, which means that a bending moment acts on the push rod. As a result, the push rod must have a certain rigidity to take this bending moment into consideration, and this inevitably makes the push rod thicker, and increases the overall weight.
A link type front suspension unit of the present invention for solving the above problems has a steering stem rotatably attached to a head pipe, a top bridge provided on an upper end of this steering stem and a bottom bridge provided on a lower end of the steering stem, a front fork supported by the top bridge and bottom bridge, and a lower end of a shock absorber supported by a link mechanism provided on the front fork, wherein the link mechanism is a quadrilateral link mechanism comprising an upper link with one end connecting to a middle part of the front fork, an axle support arm with one end connecting to a lower end of the front fork and the other end connecting to an axle side of a front wheel, and a push rod having an upper end connecting to the other end of the upper link and a lower end connecting to the axle support arm.
With this structure, it is possible to reduce a bending moment acting on the push rod.
Preferably, a side section of the front fork pipe and the upper link are parallel to a greater extent than a pivot point of the push rod of the axle support arm. As a result, it is possible to completely do away with the bending moment acting on the push rod.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.